As an image display device substitutable for liquid crystal display (LCD), image display devices with the use of technology such as an electrophoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method are proposed.
As for these image display devices, it is conceivable as inexpensive visual display device of the next generation from a merit having wide field of vision close to normal printed matter, having smaller consumption with LCD, or having a memory function, and spreading out to a display for portable device and an electronic paper is expected. Recently, electrophoresis method is proposed that microencapsulate dispersion liquid made up with dispersion particles and coloration solution and dispose the liquid between faced substrates, and also it is expected.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking imaging repetition stability, because particles with high specific gravity of titanium oxide is scattered within solution of low specific gravity, it is easy to subside, difficult to maintain a stability of dispersion state. Even in the case of microencapsulating, cell size is diminished to a microcapsule level in order to make it hard to appear, however, an essential problem was not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method wherein electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution is proposed. [The Imaging Society of Japan “Japan Hardcopy '99” (Jul. 21-23, 1999) Transaction Pages 249-252] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly dissipate charges from the electro-conductive particles, and thus there is a drawback on the lack of stability.
As one method for overcoming the various problems mentioned above, an image display device comprising an image display panel is known, which has one or more cells formed in an isolated manner from one another by partition walls and accommodating image display media and a plurality of image display elements, in which the image display media are sealed between opposed two substrates, at least one of the two substrates being transparent, and, in which the image display media, to which an electrostatic field is applied, are made to move so as to display an image.
As one example, in the image display device, the partition walls are formed by: laminating a dry-film resist on one of the substrates (or substrates with electrodes) e.g. on an ITO glass substrate as the transparent substrate; performing a pattern exposure through a mask by means of i-line parallel light; developing it by using a sodium carbonate solution; washing it by using a purified water; and drying it. Here, the i-line means ultraviolet rays having a wavelength of 360 nm used as a light source of an exposure device, as is known in the prior art. After that, the image display panel is formed by: applying an adhesive on the partition walls; and connecting the other substrate e.g. opposed substrate to the partition walls through the adhesive. In the method of manufacturing image display device mentioned above, a technique is generally known such that the substrates and the partition walls are connected by using a hot-melt adhesive and a reaction type hot-melt adhesive as the adhesive (for example, Japanese Patent Laid-Open Publication No. 2002-296622).
However, there is a drawback such that an adhesion property to the glass used as the substrate is not sufficiently obtained if using the hot-melt adhesive or the reaction type hot-melt adhesive. As a result, in various endurance tests (heat-resistant test, humidity test), there is a drawback such that the adhesion property is decreased remarkably. Moreover, if using such liquid-like adhesives, there is a drawback such that the image display media remaining on the partition walls can not be removed due to the adhesive on the partition walls in the case of filling the image display media between the partition walls (tasks of a first aspect of the invention).
Moreover, in the method of manufacturing the image display device mentioned above, a connection between the partition walls formed on one substrate and the other substrate is performed by using the adhesive. In this case, since a washing with respect to the substrate and the partition walls before applying the adhesive is not sufficient, there is a drawback such that a sufficient adhesion property can not be obtained. As a result, in various endurance tests (heat-resistant test, humidity test), there is a drawback such that the adhesion property is decreased remarkably (tasks of a second aspect of the invention).
As one method for overcoming the various problems mentioned above, an image display device comprising an image display panel is known, in which image display media are sealed in cells formed in an isolated manner from one another by partition walls between a front substrate and a rear substrate, at least one of two substrates being transparent, and, in which the image display media, to which an electrostatic field is applied, are made to move so as to display an image by means of Coulomb's force and so on. As one example of such image display device, in order to improve a visibility by making a color of the rear substrate or the partition walls inconspicuous in the case of an image displaying, a technique is known such that a color of a surface of the rear substrate, an overall portion or a surface of the partition walls, and so on is made for example to a color of one of the image display media (for example, Japanese Patent Laid-Open Publication No. 2002-139748).
However, among the techniques mentioned above, in the case that the overall portion of the partition walls is made to a color of one of the image display media, especially in the case that the overall portion of the partition walls is formed by a dark color such as black, if a pigment or a dye having a dark color such as black is blended in the resist, there occurs a drawback such that a light transmission property of the resist used for forming the partition walls is deteriorated. In this manner, if a light transmission property of the resist is deteriorated, there are drawbacks: such that a light is not evenly exposed to a portion at which the partition walls are to be formed by exposing and curing, when the exposure is performed through the mask; such that a possibility for causing a insufficient development, in which the partition walls are not formed according to the pattern, becomes high especially when forming high partition walls; and such that a sufficient adhesion property between the formed partition walls and the substrate can not be obtained (tasks of a third aspect of the invention).